chem. 125-126: feb. 19, 20 and march 3 experiment 3 …chem125/w09/lec06e3w09.pdf · 1 chem....
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Chem. 125-126: Feb. 19, 20 and March 3
Experiment 3 Session 2 (Three hour lab) Complete Experiment 3 Parts 2B and 3 Complete team report Complete discussion presentation
Parts 2A and 2B
Compare the properties and reactivity of thehalogens and halides
BACKGROUND INFORMATION
11A
18VIIIA
1H
1s1
2IIA
13
IIIA14
IVA15
VA16
VIA17
VIIA
2He1s2
3Li
2s1
4Be
2s2
5B
2s22p1
6C
2s22p2
7N
2s22p3
8O
2s22p4
9F
2s22p5
1 0Ne
2s22p6
1 1Na
3s1
1 2Mg
3s2
3 IIIB
4 IVB
5 VB
6VIB
7VIIB
8VIIIB
9 !
10 VIIIB
11 IB
12 IIB
1 3Al
3s23p1
1 4Si
3s23p2
1 5P
3s23p3
1 6S
3s23p4
1 7Cl
3s23p5
1 8Ar
3s23p6
1 9K
4s1
2 0Ca
4s2
2 1Sc
4s23d1
2 2Ti
4s23d2
2 3V
4s23d3
2 4Cr
4s13d5
2 5Mn
4s23d5
2 6Fe
4s23d6
2 7Co
4s23d7
2 8Ni
4s23d8
2 9Cu
4s13d10
3 0Zn
3d1 04s2
3 1Ga
4s24p1
3 2Ge
4s24p2
3 3As
4s24p3
3 4Se
4s24p4
3 5Br
4s24p5
3 6Kr
4s24p6
3 7Rb
5s1
3 8Sr
5s2
3 9Y
5s24d1
4 0Zr
5s24d2
4 1Nb
5s24d3
4 2Mo
5s14d5
4 3Tc
5s24d5
4 4Ru
5s14d7
4 5Rh
5s14d8
4 6Pd
4d10
4 7Ag
5s14d10
4 8Cd
4d1 05s2
4 9In
5s25p1
5 0Sn
5s25p2
5 1Sb
5s25p3
5 2Te
5s25p4
5 3I
5s25p5
5 4Xe
5s25p6
5 5Cs
6s1
5 6Ba
6s2
5 7
La*
6s25d1
7 2Hf
6s25d2
7 3Ta
6s25d3
7 4W
6s25d4
7 5Re
6s25d5
7 6Os
6s25d6
7 7Ir
6s25d7
7 8Pt
6s15d9
7 9Au
6s15d10
8 0Hg
5d1 06s2
8 1Tl
6s26p1
8 2Pb
6s26p2
8 3Bi
6s26p3
8 4Po
6s26p4
8 5At
6s26p5
8 6Rn
6s26p6
8 7Fr
7s1
8 8Ra
7s2
8 9Ac#
7s26d1
1 0 4 +
7s26d2
1 0 5 +
7s26d3
1 0 6 +
7s26d4
1 0 7 +
7s26d5
1 0 8 +
7s26d6
1 0 9 +
7s26d7
+ Element synthesized,
but no official name assigned
Halogens (Family VIIA)
Q. Possible oxidation states?
Answer: ______
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Halogens
Chlorine Bromine Iodine Cl2(g) Br2(l) I2(s)
Increasing molecular weight
HALOGENS
Cl2 = ChlorineExist as diatomic NONPOLAR molecules
Oxidation state = zeroOxidizing agents that react to form halides:
Cl2 + 2 e- → 2 Cl-
Halogens
The halogens will be available in water solution.
Bromine water Iodine water
• It is difficult to visually distinguish betweenbromine and iodine water.
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Color of the Halogens
DEMO
• It is possible to visually distinguish between thehalogens in hexane where each has distinct colors
Halogens
DEMO
HALIDES
Cl- in NaCl(s)
Exist as anions in salts Salt names end in ide (e.g., sodium bromide…) Oxidation state = -1.
Reducing agents
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Halides
Sodium halide (s) Sodium halide (aq)
The halides are provided as sodium salts in watersolution.
The sodium salts of the halides visually look thesame in the solid state and in aqueous solution.
Sodium salts of the halides
• One cannot visually distinguish between the different halides
Sodium Salts of the Halides
“Like attracts like”
• are soluble in polar solvents (e.g., water). are NOT soluble in non-polar solvents (e.g.,hexane).
DEMO
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Solvent Extraction
1 - Bromine water + NaBr + hexane2- Addition of AgNO3 to test for Br- ions.
DEMO
Part 2B. Reactivity of the Halogens and Halides.
Collect experimental data on the reactivity: - oxidizing agent strength of the halogens - reducing agent strength of the halides.
Discussion questions 3 and 4, p.104
Compare the halogen reactivity data versus: - periodic table position - electronegativity values
OA Strength of Chlorine versus Bromine?
NO•Br2
NO•Cl2
•Br-•Cl-
Table: Oxidizing agents on one side andreducing agents on the other side.
SeeexpandedTable 5,p.84
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Caution: Check data. Does it make sense?
NONoBr2
NoNOCl2
Br-Cl-
“ These results don’t make sense!”
One combination of halogen and halide should react-- the stronger OA and RA agent!
Check Data. Does it make sense?
1) Cl2 + 2 Br- → 2 Cl- + Br2
RA OA
1) OA strength: ___ >___
2) OA strength: ___ >___
OA RA
2) Br2 + 2 Cl- → 2 Br- + Cl2
“Reaction 1) or 2) should occur!”
IA IIA IIIB IVB VB VIB VIIB VIIIB IB IIB IIIA IVA VA VIA VIIA
H
2.1
Li
1.0
Be
1.5
B
2.0
C
2.5
N
3.0 O
3.5
F
4.0 Na
0.9
Mg
1.2
Al
1.5
Si
1.8
P
2.1
S
2.5
Cl
3.0
K
0.8
Ca
1.0
Sc
1.3
Ti
1.5
V
1.6
Cr
1.6
Mn
1.5
Fe
1.8
Co
1.8
Ni
1.8
Cu
1.9
Zn
1.6
Ga
1.6
Ge
1.8
As
2.0
Se
2.4
Br
2.8
Rb
0.8
Sr
1.0
Y
1.2
Zr
1.4
Nb
1.6
Mo
1.8
Tc
1.9
Ru
2.2
Rh
2.2
Pd
2.2
Ag
1.9
Cd
1.7
In
1.7
Sn
1.8
Sb
1.9
Te
2.1
I
2.5
Cs
0.7
Ba
0.9
La
-Lu
Hf
1.3
Ta
1.5
W
1.7
Re
1.9
Os
2.2
Ir
2.2
Pt
2.2
Au
2.4
Hg
1.9
Tl
1.8
Pb
1.8
Bi
1.9
Po
2.0
At
2.2
Fr
0.7 Ra
0.9
Ac
1.1
Th
1.3
Pa
1.5
U
1.7
Np-
N o
1.3
Q. Based soley on electronegativity values,compare Cl2 and Br2 as oxidizing agents?
OA: ______>_________
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Br-Br2
Cl-Cl2
Reducing AgentOxidizing Agent
Q. Given the fact that Cl2 > Br2 as an oxidizingagent, indicate the comparative reducing agentstrength of Cl- and Br-
?
Answer.______________________________
Q. Will reaction 1) or 2) below spontaneously occur? 1) Cl2(aq) + NaBr (aq) → ?
2) Br2(aq) + NaCl(aq) → ?
Br-Br2
Cl-Cl2
Reducing AgentOxidizing Agent
Check data. Does it make sense?
NONoBr2
YESNOCl2
Br-Cl-
“ These results make sense!”
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Experiment Methods
• Compare color of hexane phase in the reactionmixture to that of known halogens (Part 2A) inhexane to identify the halogen
Br2 (aq) + NaCl (aq) + hexane→ ?
Add Br2 to NaCl + hexane Mix the phases
Br2 (aq) + NaCl (aq) + hexane→ ?
Q. Has reaction occurred? B
Cl2 Br2 I2
______
• After mixing the phases, determine the identity ofthe halogen present in the hexane phase
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Q. Record the identity of the species present in thephases upon addition of hexane to the reaction mixture.
__
___
Br2 (aq)+ 2 NaCl (aq) ____________
Q. From results rank the strength of the reducingagents (halides) and the oxidizing agent (halogens).
Br2 (aq)+ 2 NaCl(aq) _________
RA: ______> _______ OA: ______> _______
Part 3. Analysis of Redox Reactions
Identify reactants and spectators in redox rxns.
- Non-reactive redox species (K+, Na+, NO3- ) make
good substitutes for an omitted species in tests.
Identify products; write a net reaction- Compare products properties to known substances; refer to the CRC Handbook.
Rank the oxidizing or reducing agent strengthof reaction species
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“Help. I spilled Iodine!”
Example: I2 + SnCl2 → ?
DEMO:
Example: I2 + SnCl2 → ?
SnCl2(aq) + I2(aq) → clear and colorless product
Analysis of Reaction1. Record Observations
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2. Identify spectator and reactant species.
Reaction: SnCl2(aq) + I2(aq) → ?
Reference Blank Test:
NaCl(aq) + I2(aq) _________
Conclusion:
DEMO
______________
Reaction: SnCl2(aq) + I2(aq) → ?
Reference Blank Test:
Sn(NO3)2(aq) + I2(aq) ________
Conclusion: __________________
3) Identify the oxidizing and reducingagent reactants.
Reactants: Sn2+
(aq) + I2(aq)
_______________________
Reaction: SnCl2(aq) + I2(aq) → ?
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4) Identify Products and Write a Net Reaction
Observation: Light brown I2(aq) color fades.
I2(aq) → _______________ Sn2+(aq) +
Knowledge: Sn2+ is a reducing agent.
and thus must form ____________
and thus must form ________________
Sn2+aq) + I2(aq) → ____ (aq) + 2I - (aq)
RA OA ____ ____
5). Strength of the Reducing and Oxidizing Agents?
RA strength: ____ >___ OA strength: ___ >___
“The reactants are the stronger OA and RA”.
Experiment 3 Exam Question
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List the OA species and indicate OA strength:
OA F2 Co3+
Br2
K+
Exam Q. Identify the reactants in the reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
List the RA species and indicate comparativestrength:
OA F2 Co3+
Br2
K+
Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br -
K
Note (circle) all species actually present in thereaction mixture.
OA F2
Co3+
Br2
K+
Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
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Identify the species combinations that will react.
OA F2
Co3+
Br2
K+
Q. Identify the reactants in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
Answer: ___________ will react.
OA F2 Co3+
Br2
K+
Q. Identify the products in the redox reaction,CoF3(aq) + KBr(aq) → ?
given OA Strength: F2 > Co3+ > Br2 > K+
RA F-
Co2+
Br-
K
Answer: ______________
Chem 125/126 Hourly I Exam
Practice exam questions!You should be able to answer all hourly I examquestions upon completion of experiment 3.Exams on Ctools and the course web site:http:www.umich.edu/~chem125